A new review of existing scientific evidence has concluded that childhood vaccines are safe and don't cause serious health problems such as autism or leukemia.

"Our findings support that vaccines are very safe for children, and add to a substantial body of evidence that the benefits of vaccination outweigh the very low risks," said senior author Dr. Courtney Gidengil, an associate physician scientist at RAND Corporation and an instructor at Harvard Medical School. "Hopefully, this will engage hesitant parents in discussions with their health care providers."

The review found strong evidence that the MMR (measles, mumps and rubella) vaccine is not associated with autism, which is consistent with previous reviews of this rumored link.

Some parents have chosen not to have their children vaccinated because of a now-debunked and retracted study published in 1998 that suggested that the MMR vaccine might cause autism. It was later reported that the study's author, Dr. Andrew Wakefield, had altered some of the study's results.

The researchers behind the new study also found no link between childhood leukemia and vaccines for MMR, DTaP (diphtheria, tetanus and pertussis), tetanus, influenza and hepatitis B.

Overall, vaccines given to children 6 or younger are safe, causing few side effects, the review concluded. The findings are published in the July 1 online edition and the August print issue of the journal Pediatrics.